Among the most visible are Aprilis Inc., a Polaroid spin-off based in Maynard, Mass., and InPhase Technologies Inc., a Lucent Bell Labs venture in Longmont, Colo. Both are developing the high-density, high-transfer-rate technology that researchers believe has the potential to revolutionize data storage and enable rapid distribution of digital content.

Elsewhere, organizations like IBM Corp.'s Almaden Research Lab continue holographic data storage (HDS) research for internal purposes, and several Japanese consumer electronics companies are devising holographic drive products based on media they have purchased from either of the two U.S. startups.

Both Aprilis and InPhase Technologies have gone public in the past year, claiming advancements in their technology that the companies assert could bring HDS closer to the mainstream-and commercial products to market-in approximately two to three years.

But progress has proved more difficult than early boosters imagined, and applications begging for HDS remain few and far between. "There is some interest in write-once memory for archival storage of data that is stored once and never changed," said James Porter, principal of research firm Disk Trend Inc. (Mountain View, Calif.). "But it is a small segment of the storage market typically addressed by tape and optical-disk drives."

To replace tape and optical drives in applications such as finance and geophysical maps for oil exploration, where databases store large image files that are not touched again, developers must bring down the price of HDS technology. "The companies need to demonstrate scheduled producibility, reliability and price competitiveness on a price-per-byte-stored [basis] with comparable products," Porter said.

Aprilis and InPhase claim to be meeting at least some of these objectives. Wolfgang Schlichting, research manager in the storage mechanism program at International Data Corp. (Framingham, Mass.), confirmed that the two have made significant progress but added that "it will take some more time for the products to be developed."

Aprilis, whose media technology is based on a material developed at Polaroid in the 1990s, claimed early this year to have achieved a milestone recording density of 100 Gbits per square inch on its storage media.

Schlichting confirmed that the company showed a "significant density improvement" after fine-tuning its process. But Aprilis now needs to show major gains over existing technology "in order for the broader market to be convinced" of holography's potential, he said.

"People won't just jump on new [HDS] products just because of their promise," Schlichting said, adding that holography will have to outpace developments in competing technologies, "which will also have moved on" by the time HDS products are ready for prime time.

Aprilis presented a paper at the International Society of Optical Engineering conference in January describing its ability to record 100 Gbits/inch2 on its holographic storage media, chief executive officer and president John Berg told EE Times.

Aprilis manufactures a limited volume of holographic media, the HMD and HMC series, for about 15 customers developing their own holographic drives and drive products. In both product lines, the company's proprietary high-performance recording medium is sandwiched between two unformatted glass substrates. The HMD series comes in a 120-mm-disk format; HMC-series media are available in a 50 x 50-mm card format. Both are readily available in two standard recording thicknesses: 200 and 300 microns.

Aprilis says it is able to reproduce its media at its manufacturing facilities in a 60-second cycle time, and envisions media products for high- and low-end markets. The company foresees fielding an extremely flat, flawless disk that would cost between $40 and $200 at the high end, along with a less-expensive, less-perfect disk for the low end. The low-end media would use special technologies to compensate for "wedge" or "tilt" in the disk and would sell for $2 to $5.

Aprilis has achieved a milestone recording density of 100 Gbits per square inch on its storage media.

Berg believes holographic storage advances will soon outstrip technologies like the Blu-ray Disk format being promoted in Japan for next-generation DVD in certain applications, such as those designed for the 20- to 100-Gbyte capacity range. He also estimates that in two years, holographic media will be the media of choice for write-once archival applications, because "it's more convenient and not subject to the wear and tensioning" that plague tape drives.

Aprilis says it is co-developing its own holographic drives with partners and claims that its media customers are separately developing holographic storage drives of their own.

InPhase Technologies, which was spun out of Lucent Bell Labs in 2000, possesses 40 Bell Labs patents associated with holographic technology and says it has filed for 30 of its own. The company has created a holographic recording medium called Tapestry based on a Bell Labs photopolymer.

To fabricate it, InPhase designed an automated bonding and media-handling system, which it demonstrated in April 2002. The company maintains that its manufacturing process, known as ZeroWave, makes it possible to use inexpensive substrates similar to those used in DVD manufacturing to create flat, holographic media. InPhase has demonstrated recording and playback of digital video on its media and plans to show recording and reading of digital video and audio files at the National Association of Broadcasters convention in April.

With those achievements under its belt, InPhase Technologies says it will use is a $2 million grant from the Advanced Technology Program of the National Institute of Standards and Technology, awarded in December, to develop rewritable recording media. Also on the company's road map is a recordable drive with target specifications of 200 Gbytes and 20 Mbytes/second. Lisa Dhar, vice president of media development, did not give an estimated date for launch of the latter development.

As the two U.S. startups work toward their first real revenues from HDS products, Aprilis has bolstered its intellectual-property portfolio by acquiring HDS-related IP from defunct HDS research projects. It plans to sell technology licenses to customers already using its holographic storage media as well as to competitors. "We want to be in the business of promoting commercialization of holography," said CEO Berg.

Aprilis holds licenses to three Polaroid patents and has 10 of its own patents pending. In December, it purchased 21 patents from Manhattan Scientifics Inc. (New York and Los Alamos, N.M.) related to the composition of the holographic media and the drive implementation. Early this year Aprilis acquired 13 more patents related to holographic recording hardware and drive servo from Holoplex Technologies Inc. (Pasadena, Calif.).